Previously when pipes were coated, an outer pipe was first formed on top of the pipe to be coated. In such a case, it was not possible to provide the outer pipe with the desired orientation, for example. Further, when a long screw is used in the present manner, the pipe to be coated warms up.
Norwegian Published Specification 159,841 discloses a crosshead tool provided with a rotating mandrel in connection with the extruder. With this arrangement, it is possible to form, but not maintain, the desired orientation during the coating of a cable, even though the coating layer can be pressed at least in principle against the cable with pressure, so that the adhesion of the coating to the surface to be coated can be improved.
The purpose of the present invention is to avoid prior art problems and to produce an extrusion apparatus that provides the product with the primarily desired permanent orientation.